A crankshaft in a vehicle translates the reciprocating linear motion of an engine's pistons into rotational motion. In so doing, torsional vibrations are generated that emanate through out the vehicle. A four cycle engine with 8, 6, or 4 cylinders tends to produce (respectively) 4, 3 or 2 combustion pulse accelerations per engine revolution. These combustion pulses tend to accelerate the crank and driveline at a frequency that is a multiple of 4, 3 or 2 of the average rotational speed of the engine. Vibrations generated as a result of these pulsations may be uncomfortable for the operator and/or passengers of the vehicle and are unwanted. To reduce the vibrations, the crankshaft may have a frequency tuned dampener that counteracts vibrations at certain frequencies. However, the frequency tuned dampener only operates at one frequency and does not reduce vibrations that occur at other frequencies.
Alternatively, one or more pendulums, with a properly calibrated path of travel, may be attached to the crankshaft at a calibrated distance from its center of rotation. Pendulums, also known as pendulum absorbers or torsional absorbers, act to reduce torsional vibrations that occur at a frequency that is a specific order or multiple of average engine speed. The pendulums are often connected such that they swing (cyclically or non-cyclically) within a predetermined range of motion during the operation of the engine. It is possible for the metallic pendulums to make contact with other portions of the metallic crankshaft, particularly when absorbing severe torsionals. As such, stop pads or other end-of-travel stops are required to reduce noise and to prevent damage to the pendulum or the crankshaft components.
Today's stops, however, are not without their shortcomings. For example, the stops are usually made of non-metallic material, which means that they will eventually become worn out or damaged by the contact with the pendulum. Moreover, contact between the pendulum and stops will result in some undesirable noise, which will worsen over time as the stops begin to wear down. Accordingly, the inventors herein have recognized a need for improvement in the art.